ASIM'S WEBWORLD View: Main School Main AP Biology Chapter Guides RELATED LINKS Chapter Outline		AP BIOLOGY: Chapter Eight Review Answers 1. An anabolic reaction synthesizes products with energy; a catabolic reaction breaks down products with an accompanying release of energy. 2. The two states of energy are kinetic and potential. Kinetic energy is actively engaged in work; potential energy is stored energy. 3. Oxidation occurs when a molecule loses an electron; reduction is when a molecule gains an electron. These two must occur together because every electron that is lost by one molecule must be gained by another. Oxygen is one of the most common electron acceptors in a redox reaction. 4. The First Law of Thermodynamics states that energy can be changed from one form to another (potential to kinetic) but can't be lost or gained. The Second Law of Thermodynamics states that entropy increases, where entropy is energy so random and dissipated that it can't be used for work. 5. Heat is the energy of random molecular motion. Entropy is a tendency toward disorder in the universe. Free energy is the energy present in the chemical bonds of a molecule, minus the energy lost to entropy. 6. In exergonic reactions, products contain less energy or more disorder than the reactants, release energy, and proceed spontaneously. In endergonic reactions, products contain more free energy or more disorder than reactants and require an input of energy to proceed. 7. Activation energy is the energy required to get spontaneous reactions going. It keeps spontaneous reactions under some control to prevent reactions from immediately going to the maximum. If there is high activation energy, there is a slow reaction rate; with a low activation energy, there is a fast reaction rate. Catalysts lower the activation energy required for a reaction to get started and will provide for a greater amount of reactant converted into product. 8. Enzymes typically function at an optimum range of temperature and pH. Above or below these ranges the reaction may be slowed or halted altogether if the protein (enzymes are proteins) becomes denatured. When an enzyme is denatured, it unfolds and loses its catalytic ability. 9. The active site on an enzyme is where the substrate binds. An allosteric site is where a non-competitive enzyme inhibitor would bind, effecting a change in the shape of the enzyme so that it could no longer bind the substrate. A competitive inhibitor binds to the actual substrate-binding domain of the enzyme. 10. Many enzymes require binding by cofactors or coenzymes before they can catalyze their specific reactions. 11. The high-energy bonds between the phosphate groups liberate the most energy when they are cleaved. Cleaving those bonds liberates 7.3 kcal of energy, which represents about twice the activation energy of most cellular reactions. 12. A sequential series of reactions inside a cell is called a biochemical pathway. The final reactions are thought to have evolved first because pathways evolve backward, adding new steps at the beginning.